1. Field of the Invention
The field of the invention relates generally to adaptive learning for engine exhaust gas sensors.
2. Background of the Invention
Engine control systems utilize adaptive learning to correct sensor readings, or compensate for component wear. In particular, exhaust gas sensors coupled to an engine exhaust are typically used for such adaptive learning. For example, the sensor reading can be used to correct for air-flow measurement errors, and changes in fuel injectors due to aging.
The inventors herein have developed an engine control methodology that allows efficient engine operation with some of the cylinders inducting air with no injected fuel. The inventors have also found that when using such a system with conventional adaptive learning methods, degraded results are obtained. For example, when the system includes exhaust gas sensors exposed to air from cylinders without injected fuel, there is no information as to the amount of fuel injected into other cylinders, and thus no information to be had from that adaptation algorithm. As such, when the algorithm attempts to incorporate this sensor data, degraded results are obtained.
The above problem is solved by a system comprising an engine having a first and second group of cylinders, a sensor coupled to at least one of the first and second groups, and a controller for operating the engine in two modes. In a first mode, the engine is operated with a mixture of air and substantially no injected fuel in the first combustion group and with air and injected fuel in the second combustion group and in a second mode the engine is operated where both of the first and second groups combust a mixture of air and injected fuel. The controller disables adaptive learning of the sensor during the first mode and enables adaptive learning during the second mode.
In particular, by disabling adaptive learning from the sensor that is exposed only to air from cylinders without injected fuel, the adaptation algorithm can operate properly.